#define  _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
int main()
{
	double s = 0;
	scanf("%lf", &s);
	double i = 2.0;
	int count = 1;
	double sum = i;
	while (sum < s)
	{
		sum = i * 0.98 + sum;
		i *= 0.98;
		count++;
	}
	printf("%d", count);
	return 0;
}